解方程组xy/(x+y)=6/5① yz/(x+z)=12/7 ② xz/(x+z)=4/3,

解方程组xy/(x+y)=6/5① yz/(x+z)=12/7 ② xz/(x+z)=4/3,
解方程组xy/(x+y)=6/5① yz/(x+z)=12/7 ② xz/(x+z)=4/3,

解方程组xy/(x+y)=6/5① yz/(x+z)=12/7 ② xz/(x+z)=4/3,
xy/(x+y)=6/5① ---->(x+y)/(xy)=5/6 1/x+1/y =5/6 (4)
yz/(y+z)=12/7 ② 1/y+1/z= 7/12 (5)
xz/(x+z)=4/3 1/x +1/z=3/4 (6)
（4）+（5）+（6）得
1/x+1/y+1/z=13/12 (7)
(7)-(5)得 x=2
(7)-(6) 得 y=3
(7)-(4)得 z=4